GB2238190A

GB2238190A - Electrical energy store for operating a circuit breaker

Info

Publication number: GB2238190A
Application number: GB9022584A
Authority: GB
Inventors: John Layton Davenport
Original assignee: GEC Alsthom Ltd
Current assignee: GE Power UK
Priority date: 1989-10-27
Filing date: 1990-10-17
Publication date: 1991-05-22
Also published as: GB9022584D0; MTP1072B; CA2028388A1; JPH03155332A; EP0425169A3; CN1052398A; EP0425169A2; ZA908592B; GB8924238D0; US5093770A; AU6495390A

Description

-> 2:3 -1. C3 G) Electrical Energy Storage System This invention relates

to circuit arrangements for providing a store of electrical energy for actuating an electrically operable device, more especially for altering the state of a magnetic actuator in order to effect the opening or closing of an associated circuit breaker.

Such a circuit arrangement may, for example, incorporate a large reservoir capacitor which, when fully charged, stores sufficient energy to permit several close/open operations constituting an auto-reclose cycle of the circuit breaker, ending in the circuit breaker locked out in the open position, in the event of a fault in the line controlled by the circuit breaker to clear by the end of the cycle.

A typical auto-reclose cycle can, for example, take the form o-tco-t'-co-t"-co or alternatively where co-t-co-C-co-t 11-CO c = closing operation o = opening operation, and t, V, C are increasing time intervals in the range 0.3 to several seconds, which can be set as required. After the cycle has been completed, a relatively long time interval, of the order of minutes, would then be available for re-charging of the reservoir capacitor in readiness for further operations.

Although re-charging of the reservoir from a conventional voltage transformer and rectifier connected to the supply side of the circuit breaker is technically sound, it incurs considerable expense in order to provide the relatively low power required for this purpose.

Accordingly an object of the invention is to provide a low power charging source from high voltage conductors of a supply line, using components which in total are less expensive than a conventional voltage transformer.

According to the invention a circuit arrangement for providing a store of electrical energy for actuating an electrically operable device, incorporating a reservoir capacitor, comprises a transformer having low resistance windings, the primary winding of which is connectable to an alternating current high voltage supply in series withat least one reactance capacitor, and the secondary winding of which is connected to the reservoir capacitor through a rectifier, the capacitor being connectable to said electrically operable device, with the turns ratio of the transformer such as to produce a secondary current of sufficient magnitude to charge the reservoir capacitor in the time available for successive operations or successive operational sequences of the device.

In the application of the circuit arrangement to the operation of magnetic actuators for effecting close/open operations of an associated circuit breaker, the reservoir capacitor must, of course, be capable of storing sufficient energy to permit the required number of close/open operations in the auto-reclose cycle, and the charging current must be adequate to permit charging of the reservoir capacitor in the time available between successive auto-reclose cycles.

The magnetic actuator may, for example, be of the construction described in co-pending Patent Application No. 8918416.2 (Serial No. 2223357A).

Where the primary winding of the transformer, which can take the form of a current transformer, is connected between two high 1 voltage conductors, the winding is preferably connected to each of the conductors through a respective reactance capacitor.

However where the primary winding is connected between a high voltage conductor and an earth conductor, the primary winding can be connected directly to the earth conductor, a single reactance capacitor being connected between the primary winding and the high voltage conductor.

The voltage to which the reservoir capacitor is charged is conveniently determined by a Zener diode connected in parallel with the reservoir capacitor, although other means of achieving this may alternatively be employed as will subsequently be described.

One circuit arrangement in accordance with the invention, for use in charging a capacitor capable of storing electrical energy for the operation of a magnetic actuator designed to produce a number of close/open operations of an associated circuit breaker, for example as described in co-pending Patent Application No. 8918416.2, will now be described by way of example with reference to the accompanying drawing.

In this circuit arrangement the primary winding P of a current transformer T is connected between a pair of high voltage alternating current supply conductors H1, H2 a capacitor C1 being connected between each end of the primary winding and the respective supply conductor H1, H2. The primary current il of the transformer is defined almost entirely by the reactance of the two series capacitors C1.

The secondary winding S of the transformer T is connected to a reservoir capacitor C2 through a full wave rectifier R, and the reservoir capacitor C2 is connected, in turn, to the magnetic actuator control circuit. The construction of the magnetic actuator and the control arrangements therefor are not relevant to the present invention, but may be as described in Patent Application No. 8918416.2.

A current transformer suitable for such a purpose has a primary winding P of 5000 turns, a secondary winding 5 of 1000 turns, and a laminated iron core with a cross-sectional area of 900 mm2.

A Zener diode Z is connected across the reservoir capacitor C2 to determine the voltage to which the capacitor is finally charged, the Zener diode then conducting the secondary current 12 from the rectifier R. The turns ratio of the transformer T is chosen to produce a secondary current i2 which is of sufficient magnitude to charge the reservoir capacitor C2 in the time available between successive auto- reclose cycles of the circuit breaker. The reservoir capacitor conveniently has a nominal capacity 10,000AiF, and is arranged to be charged to a voltage of 38OV determined by the Zener diode Z, to give an energy storage of 700 joules for an auto-reclose cycle as above described to be completed without recharging being required.

The circuit as above described was tested for line voltages of 120, 15kV and 27kV, the transformer design remaining the same in each case. The capacitors Cl were each 0.024juF for the 120 line voltage and proportionally less for the 150 and 270 line voltages to give a primary current il=0.045A. Part of this primary current is required for magnetising the transformer core and the remainder, increased by the 5:1 turns ratio, is converted to a rectified secondary current i2_-0.17A. The time to charge the capacitor C2 from zero to 38OV was found to be 35 seconds, which is well within the time required for starting a further auto-reclose cycle.

In place of the Zener diode Z electronic means, as indicated by the broken lines A, may be built into the circuit to short circuit the rectified supply at the output of the rectifier R when the reservoir capacitor C2 is fully charged, and to re-establish the supply when the voltage has decreased by a certain amount, either by leakage or on operation of the actuator. Where such an electronic means is employed the reservoir capacitor will normally voltage cycle between an upper and a lower limit, a diode, as at D, then being provided to prevent discharge of the capacitor into the short circuit when applied.

The primary winding P of the charging circuit transformer T may alternatively be connected between one high voltage line and earth, in which case a single capacitor Cl only, with a suitably changed capacitance value, need be connected between the primary winding and the high voltage line, the other end of the primary winding being connected directly to an earth conductor.

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Claims

CLAIMS 1. A circuit arrangement for providing a store of energy for actuating an electrically operable device, incorporating a reservoir capacitor, comprising a transformer having low resistance windings, the primary winding of which is connectable to an alternating current high voltage supply in series with at least one resistance capacitor, and the secondary winding of which is connected to the reservoir capacitor through a rectifier, the capacitor being connectable to said electrically operable device, with the turns ratio of the transformer such as to produce a secondary current of sufficient magnitude to charge the reservoir capacitor in the time available for successive operations or successive operational sequences of the device. 2. A circuit arrangement according to Claim 1 in combination with a circuit breaker, and a magnetic actuator for effecting automatic close/open operations of the circuit breaker, wherein the reservoir capacitor is capable of storing sufficient energy to permit a predetermined number of close/open operations in the auto-reclose cycle, the charging current being adequate to permit charging of the reservoir capacitor in the time available between successive auto-reclose cycles. 3. A circuit arrangement according to Claim 2 wherein the magnetic actuator is as claimed in Claim 4 of GB 2223357A. 4. A circuit arrangement according to Claim 1, 2 or 3 wherein the transformer is a current transformer. 5. A circuit arrangement according to any one of claims 1 to 4 wherein the primary winding of the transformer is connected between two high voltage conductors, each end of the winding being connected to a conductor through a respective capacitor. 6. A circuit arrangement according to any one of Claims 1 to 4 wherein the primary winding is connected between a high voltage conductor and an earth conductor, the respective end of the primary winding being connected to the high voltage conductor through a capacitor, and the opposite end of the winding being connected directly to the earth conductor. Z 7. A circuit arrangement according to any preceding claim wherein a Zener diode is connected in parallel with the reservoir capacitor. 8. A circuit arrangement according to any one of Claims 1 to 6 including electronic means operable to short circuit the rectified supply at the output of the rectifier when the reservoir capacitor is fully charged and to re- establish the supply when the voltage has decreased by a predetermined amount, a diode being connected into the circuit to prevent discharge of the capacitor into the short circuit when applied. 9. A circuit arrangement for providing a store of energy substantially as shown in and as hereinbefore described with reference to the accompanying drawing.

1 9 -AL- Amendments to the claims have been filed as follows A circuit arrangement for providing a store of energy for actuating an electrically operable device, incorporating a reservoir capacitor, comprising a transformer having low resistance windings, the primary winding of which is connectable to an alternating current high voltage supply in series with at least one reactance capacitor, and the secondary winding of which is connected to the reservoir capacitor through a rectifier, the capacitor being connectable to said electrically operable device, with the turns ratio of the transformer such as to produce a secondary current of sufficient magnitude to charge the reservoir capacitor in the time available for successive operations or successive operational sequences of the device.

2. A circuit arrangement according to Claim 1 in combination with a circuit breaker, and a magnetic actuator for effecting automatic closelopen operations of the circuit breaker, wherein the reservoir capacitor is capable of storing sufficient energy to permit a predetermined number of closelopen operations in the auto-reclose cycle, the charging current being adequate to permit charging of the reservoir capacitor in the time available between successive auto-reclose cycles.

3. A circuit arrangement according to Claim 2 wherein the magnetic actuator is as claimed in Claim 4 of GB 2223357A.

4. A circuit arrangement according to Claim 1, 2 or 3 wherein the transformer is a current transformer.

5. A circuit arrangement according to any one of Claims 1 to 4 wherein the primary winding of the transformer is connected between two high voltage conductors, each end of the winding being connected to a conductor through a respective capacitor.

6. A circuit arrangement according to any one of Claims 1 to 4 wherein the primary winding is connected between a high voltage conductor and an earth conductor, the respective end of the primary winding being connected to the high voltage conductor through a capacitor, and the opposite end of the winding being connected directly to the earth conductor.

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7. A circuit arrangement according to any preceding claim wherein a Zener diode is connected in parallel with the reservoir capacitor.

8. A circuit arrangement according to any one of Claims 1 to 6 including electronic means operable to short circuit the rectified supply at the output of the rectifier when the reservoir capacitor is fully charged and to re- establish the supply when the voltage has decreased by a predetermined amount, a diode being connected into the circuit to prevent discharge of the capacitor into the short circuit when applied.

9. A circuit arrangement for providing a store of energy substantially as shown in and as hereinbefore described with reference to the accompanying drawing.

Published 1991 at The Patent OffIce. State House, 66/71 High Holborn. LondonWC I R41T Further copies Tnay be obtained from Salts Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys. Nm-port, NPI 7HZ Printed by Multiplex techniques ltd. St Mary Cray, Kent.